diff --git a/src/fastmcp/client/transports.py b/src/fastmcp/client/transports.py
index 2cadd0631..92c88a0de 100644
--- a/src/fastmcp/client/transports.py
+++ b/src/fastmcp/client/transports.py
@@ -748,6 +748,7 @@ class UvxStdioTransport(StdioTransport):
         env: dict[str, str] | None = None
         if env_vars:
             env = os.environ.copy()
+            env.update(env_vars)
 
         super().__init__(
             command="uvx",